Background: Emergency medical service (EMS) utilization has an impact on response time, triage and primary medical treatment in Acute Coronary Syndrome (ACS) patients. However, it is currently employed mostly in higher risk patients. We hypothesized that EMS usage is a marker for increased risk for adverse outcomes in ACS patients, and therefore can be used to enhance the predictive value of the validated GRACE score.
Methods: Data from the Acute Coronary Survey in Israel registry (ACSIS) 2000-2010 was used to classify ACS patients according to EMS use. GRACE score was calculated upon admission, and GRACE risk estimation for mortality and MACE (as continuous or dichotomous variable with cutoff of 140) was adjusted by EMS use.
Results: The study population comprised of 10724 ACS patients, among whom 5576 (52%) used EMS. Patients that used EMS when compared to self-arrivals had significantly higher rates of in hospital mortality (4.4% vs. 1.7%, p<0.0001), 7 days mortality (4.5% vs. 1.9%, p<0.0001%), 30 days mortality (7.2% vs. 3.2%, p<0.0001), one year mortality (12.3% vs. 7.1% p<0.0001), and higher MACE (18.4% vs. 14.2%, p<0.0001). In a multivariable analysis, after adjustment for the GRACE score, EMS use was independently associated with increased risk hospital mortality HR 1.553 (1.094 to 2.204 ;95% CI), 7 days mortality HR 1.728 (1.217 to 2.453 ;95% CI), 30 days mortality HR 1.672 (1.289 to 2.168; 95% CI), one year mortality HR 1.389 (1.167 to 1.653; 95% CI).
Conclusion: Our findings suggest that EMS usage is a marker for an increased mortality among ACS patients, and may be used to enhance the predictive value of GRACE score for improved risk stratification.
